Monomers and homopolymers, having high photoinduceable double refraction, prepared therefrom

ABSTRACT

Homopolymers suitable for storage of information provided optically are disclosed. The are formed from monomers which  
     contain groupings which are at least trinuclear, which are capable of absorbing the electromagnetic radiation of visible light, and which are structured so that in their thermodynamically stable state they are distended and strongly anisometric,  
     wherein the at least trinuclear groupings comprise at least one electron-attracting substituent which gives rise to a dipole moment which forms an angle of at least 20° with the longitudinal axis of the at least trinuclear groupings,  
     wherein the at least trinuclear groupings contain at least one nucleus-linking group which is suitable for a photo-induced change in configuration, wherein said group is selected from the set consisting of

[0001] This invention relates to polymers comprising photo-addressableside groups, in which a high level of birefringence can be induced byirradiation, so that they are suitable for the storage of informationwhich is provided optically or are suitable as passive or opticallyswitchable components.

[0002] Various polymers comprising photochromic groups are known fromthe literature: the special peculiarity thereof is that their opticalproperties, such as absorption, emission, reflection, birefringence andscattering, can be induced by light and can be varied reversibly.Polymers of this type have a special branched structure: side groupswhich are capable of absorbing electromagnetic radiation are seated—viaparts of molecules which act as spacers—on a linear backbone. Theinterest of experts in this field has recently been directed towardsside group polymers such as these which comprise side groups ofdifferent types, one type of which is capable of absorbingelectromagnetic radiation whilst the other type is a mesogenic group,the shape of which is anisotropic. Liquid crystalline side grouppolymers of this type are described in U.S. Pat. Nos. 4,631,328 and4,943,617, for example. In their unoriented state, films of thesepolymers are turbid and scatter light; these films do not become clearand transparent until they are aligned.

[0003] Amorphous polymers which are suitable for storing opticalinformation are known from DE-OS 38 10 722 and U.S. Pat. No. 5,173,381.These have the technical advantage that films made of these polymersexhibit usable optical properties immediately after they are produced.

[0004] Homopolymers are seldom mentioned in this connection. EP-A 617110 describes azo-containing carbaminates which are renderedpolymerisable by N-acylation with (meth)acrylic acid. In actuality,homopolymers are generally inferior to copolymers.

[0005] The only processes which have been described hitherto for thereversible storage of information are those where deletion of theinformation is effected by raising the temperature, and can be effectedboth by heat and by light. Moreover, deletion by light can exhibit theadvantage that the process is limited to a defined location, which iswhy this variant is preferred. In general, it can be stated that onraising the temperature the property of retaining stored information islost. The known compounds therefore have the disadvantage that thebirefringence effects which are written in are not thermally stable. Atelevated temperatures, particularly at temperatures approaching theglass transition temperature, birefringence becomes less pronounced andfinally disappears completely. There is therefore a need for informationstorage media for which the stability of written information is asinsensitive to temperature as possible.

[0006] Surprisingly, it has now been found that superior side chainpolymers which are suitable for the production of photo-addressableinformation storage media can be produced if monomers arehomopolymerised, which

[0007] contain groupings which are at least trinuclear, which arecapable of absorbing the electromagnetic radiation of visible light, andwhich are structured so that in their thermodynamically stable statethey are distended and strongly anisometric,

[0008] wherein the at least trinuclear groupings comprise at least one,preferably at least two, electron-attracting substituent(s) whichgive(s) rise to a dipole moment which forms an angle of at least 20°.preferably at least 30°, with the longitudinal axis of the at leasttrinuclear groupings.

[0009] Thermally stable grey scales can be written into these newpolymers under the effect of light.

[0010] In principle, at least two methods of influencing the dipolemoment are possible, namely

[0011] substitution with lateral, electron-attracting substituents whichare disposed unsymmetrically with respect to the longitudinal axis ofthe grouping, and

[0012] the use of nucleus-linking polar groups, the dipole moments ofwhich do not point in the direction of their longitudinal axis.

[0013] Groups which are capable of forming hydrogen bonds with eachother, such as —NH—CO— and —OC—NH— for example, are particularlypreferred in this respect.

[0014] The expression “electromagnetic radiation of visible light”should be understood to mean light with a wavelength range from 350 to750 nm.

[0015] The expression “thermodynamically stable state” should beunderstood in the sense of the present invention to mean the lowestenergy configuration such as that which occurs in the dark in adissolved state in an organic solvent, for example. When cis/transisomerism exists, such as that which occurs with stilbenes and azocompounds for example, the trans isomer is the isomer of lower energy ineach case. The configuration which is present can be determinedspectroscopically from the absorption bands.

[0016] “Distended” in the sense of the present invention is to beunderstood to mean a state in which the at least trinuclear groupingsare situated within a cylinder with a length/diameter ratio of 2.5,preferably 3, wherein the length of the cylinder is identical to thelength of the at least trinuclear grouping.

[0017] “Strictly anisometric” in the sense of the present inventionmeans a structure in which none of the nuclei is directly or indirectlybonded (i.e. via a bonding group without a nucleus) to the next nucleus,i.e. it preferably (for trinuclear groupings) means a structure wherethe middle nucleus is a 6-membered ring which is directly or indirectlybonded via its 1- and 4-positions to the adjacent nuclei.

[0018] “Electron-attracting substituent” in the sense of the presentinvention is to be understood to mean substituents which reduce thebasicity, i.e. the electron density, of the nucleus on which they aresituated, due to induction and/or mesomeric effects. These substituentspreferably comprise alkylcarbonyl, carboxyl, alkoxycarbonyl, carbamido,carboxylamino, cyano, nitro and ammonium, and—less preferably—comprisethe halogens.

[0019] “Lateral” in the sense of the present invention can be explainedby citing the example of an azobenzene group, and denotes that thesubstituent forms an angle with the longitudinal axis of the azobenzeneand is therefore situated in the o- and/or m-position, whilst asubstituent in the p-position is not considered as being “lateral” inthe sense of the invention. If a phenyl radical of the azobenzene isreplaced by a five-membered ring, for example, the substituents are“lateral” in all conceivable positions, because on a five-membered ringthere is no position corresponding to the p-position on a 6-memberedring.

[0020] In principle, all groups which contain carboxyl groups aresuitable as nucleus-linking polar groups, the dipole moment of which isat least 200. This can be well illustrated by using the amide group asan example:

[0021] The orientation of the dipole moment of the carboxyl group formsan angle α with the longitudinal axis which is at least 20°.

[0022] The present invention also relates to homopolymers, formed frommonomers which

[0023] contain groupings which are at least trinuclear, which arecapable of absorbing the electromagnetic radiation of visible light, andwhich are structured so that in their thermodynamically stable statethey are distended and strongly anisometric,

[0024] wherein the at least trinuclear groupings comprise at least oneelectron-attracting substituent which gives rise to a dipole momentwhich forms an angle of at least 20° with the longitudinal axis of theat least trinuclear groupings.

[0025] The preferred groupings which are at least trinuclear are thosewhich contain at least two aromatic nuclei.

[0026] The preferred polymers according to the invention contain, on amain chain which acts as a backbone, covalently bonded side groups whichbranch therefrom, of formula

—S—T—Q—E  (I),

[0027] wherein

[0028] S denotes oxygen, sulphur or NR¹,

[0029] R¹ denotes hydrogen or C₁-C₄ alkyl,

[0030] T denotes a (CH₂), radical, which can optionally be interruptedby —O—, —NR¹— or —OSiR¹ ₂O— and/or which can optionally be substitutedby methyl or ethyl,

[0031] n denotes the numbers 2, 3 or 4,

[0032] Q denotes a radical comprising two bonds, and

[0033] E denotes an at least trinuclear grouping which comprises thefeatures according to the claims.

[0034] The function of the radical T is to ensure a certain spacing ofthe side group from the chain which acts as the backbone. It istherefore also termed a “spacer”.

[0035] The radical Q links the terminal group E to the spacer T, whichitself forms the bond to the main chain via bonding element S. Thespecial feature of group Q is its influence firstly on E and secondly onthe adjacent groups.

[0036] The preferred radicals Q comprise the groups —S—, SO₂—, —O—,—COO—, —OCO—, —CONR¹—, —NR¹—CO—, —NR¹— and (CH₂)_(m), where m=1 or 2.

[0037] The at least trinuclear groupings E contain at least onenucleus-linking group which is suitable for a photo-induced change inconfiguration, such as

[0038] In addition to at least one group of variable configuration, thegroupings E also contain other nucleus-linking groups, such as —C≡C—,—COO—, —OCO—, —CONR¹—, —NR¹CO— or a direct bond, wherein R¹ ispreferably R and direct bonds are less preferred.

[0039] The at least 3 nuclei of E can each represent a 5- or 6-memberedcycloaliphatic ring or a naphthalene radical, with the proviso that atleast two nuclei, and preferably at least three nuclei, are aromatic.

[0040] Nuclei of E which are particularly preferred include2,6-naphthylene and 1,4-phenylene, as well as heterocyclic radicals ofstructures

[0041] 5-membered ring systems can be carbocyclic, but are preferablyheteroaromatic and contain up to 3 hetero atoms, preferably from theseries comprising S, N, O. Examples of suitable representatives includethiophene, thiazole, oxazole, triazole, oxadiazole and thiadiazole.Heterocycles comprising 2 hetero atoms are particular preferred.

[0042] The preferred groupings E contain cinnamic acid or stilbeneradicals and azo dye radicals or analogues of a heterocyclic type,preferably mono- and diazo dye radicals.

[0043] The groupings E should be polarised. As described above, saidpolarisation can be effected by substitution with electron-attractinglateral substituents. The preferred substituents are those which haveHammett values of at least 0.5. The a values are known from theliterature; see C. Hansch, A. Leo, R. W. Taft, Chem. Rev. 1991 91(165-195). If the nuclei are multiply-substituted, the number ofsubstituents in each case depends on the number of possible positions ofsubstitution, on the options for incorporating the substituents and onthe properties of the substituted systems. The 2,4- and 3,4-positions on6-membered rings are preferred; the preferred substituents are cyano andnitro.

[0044] Aromatic nuclei which are suitable for B preferably contain 6 to14 C atoms in their aromatic ring, which can be singly- ormultiply-substituted by C₁-C₁₂ alkyl, C₁-C₁₂ alkoxy, hydroxy, halogen(particularly F, Cl or Br), amino, nitro, trifluoromethyl, cyano,carboxy, COOR (R=C₁-C₆ alkyl, cyclohexyl, benzyl, phenyl), C₅-C₁₂cycloalkyl, C₁-C₁₂ alkylthio, C₁-C₆ alkylsulphonyl, C₆-C₁₂arylsulphonyl, aminosulphonyl, C₁-C₆ alkylaminosulphonyl,phenylaminosulphonyl, aminocarbonyl, C₁-C₆ alkylamino-carbonyl,phenylaminocarbonyl, C₁-C₄ alkylamino, di-C₁-C₄ alkylamino, phenylamino,C₁-C₅ acylamino, C₁-C₄ alkylsulphonylamino, mono- or di-C₁-C₄alkylaminocarbonylamino, C₁-C₄ alkoxycarbonylamino ortrifluoromethyl-sulphonyl.

[0045] Heterocyclic nuclei which are suitable for E preferably contain 5to 14 ring atoms, 1 to 4 of which are hetero atoms from the seriescomprising nitrogen, oxygen and sulphur, wherein the heterocyclic ringsystem can be singly- or multiply-substituted by C₁-C₁₂ alkyl, C₁-C₁₂alkoxy, hydroxy, halogen (particularly F, Cl or Br), amino, nitro,trifluoromethyl, cyano, carboxy, COOR (R=C₁-C₆ alkyl, cyclohexyl,benzyl, phenyl), C₅-C₁₂ cycloalkyl, C₁-C₁₂ alkylthio, C₁-C₆alkylsulphonyl, C₆-C₁₂ arylsulphonyl, aminosulphonyl, C₁-C₆alkylaminosulphonyl, phenylaminosulphonyl, aminocarbonyl, C₁-C₆alkylamino-carbonyl, phenylaminocarbonyl, C,-C₄ alkylamino, di-C₁-C₄alkylamino, phenylamino, C₁-C₅ acylamino, C₁-C₄ alkylsulphonylamino,mono- or di-C₁-C₄ alkylaminocarbonylamino, C₁-C₄ alkoxycarbonylamino ortrifluoromethyl-sulphonyl.

[0046] Particularly preferred groupings E contain the followingbinuclear partial radicals: either one aromatic nucleus and oneheterocyclic nucleus or two aromatic nuclei.

[0047] The preferred binuclear partial radicals are azobenzene radicalsof formula

[0048] wherein

[0049] R represents a bond or nitro, or preferably represents a4-substituted benzamido or cyano, and the rings A and B can besubstituted in addition. If R represents cyano or nitro, ring A ispreferably substituted in addition, wherein the substituent should havea σ value of at least 0.5.

[0050] Azobenzene radicals which are particularly preferred correspondto the formula

[0051] wherein

[0052] R² to R⁶, independently of each other, represent hydrogen,chlorine, bromine, trifluoromethyl, methoxy, SO₂CH₃, SO₂CF₃, SO₂NH₂,preferably CN, 4-substituted benzamido or nitro, preferably with theproviso that at least two of these radicals are not hydrogen, wherein

[0053] R⁴ can additionally denote a single bond, and

[0054] R⁷ to R¹⁰, independently of each other, denote hydrogen, chlorineor methyl.

[0055] If there is multiple substitution of ring A, the 2,4- and3,4-positions are preferred.

[0056] Therefore, the preferred groupings E correspond to the formula

[0057] wherein

[0058] R² to R⁶and R⁷ to R¹⁰ have the meanings given above, and

[0059] R², to R⁶, the have meanings of R² to R⁶, but are independentthereof.

[0060] Other binuclear partial radicals correspond to the formula

[0061] wherein

[0062] K, L and M, independently of each other, denote the atoms N, S orO, or optionally denote —CH₂— or —CH═, with the proviso that at least ofone of the members K, L or M is a hetero atom and ring A is saturated orcontains 1 or 2 double bonds, and

[0063] R², and R⁷ to R¹⁰, independently of each other, have the meaningsgiven above.

[0064] Ring A preferably represents a thiophene, thiazole, oxazole,triazole, oxadiazole or thiadiazole radical.

[0065] Other preferred groups E correspond to the formula

[0066] wherein

[0067] R² to R¹⁰ and R², to R⁶, have the meanings given above.

[0068] A common feature of the above formulae is that substitution ofring A in the 4-, 2,4- and 3,4-positions is particularly preferred.

[0069] Groupings E which are particularly preferred correspond to theformulae:

[0070] The polymers which are preferred according to the inventionsolely contain recurring units comprising side groups 1, and preferablycontain those of formula

[0071] where R=H, or preferably where R=methyl.

[0072] The corresponding preferred monomers for the introduction of sidegroups I therefore correspond to the formula

[0073] The main chain of the side group polymers is therefore formedsolely from monomers which comprise side groups (I).

[0074] The polymers according to the invention preferably have glasstransition temperatures Tg of at least 40° C. The glass transitiontemperature can be determined as described by B. Vollmer, Grundriβ derMakromolekularen Chemie, pages 406 to 410, Springer-Verlag, Heidelberg1962, for example.

[0075] In general, the polymers according to the invention have amolecular weight, determined as the weight average molecular weight,from 3000 to 2,000,000, preferably 5000 to 1,500,000, as determined bygel permeation chromatography (calibrated with polystyrene).

[0076] Due to the structure of the polymers, the intermolecularinteractions of structural elements (I) are such that the formation ofliquid crystalline states of order is suppressed, and opticallyisotropic, transparent, non-scattering films can be produced. On theother hand, the intermolecular interactions are neverthelesssufficiently strong so that irradiation with polarised light results ina photochemically induced, cooperative, directional reorientationprocess of the side groups.

[0077] Extremely high levels of optical anisotropy can be induced in theoptically isotropic, amorphous polymers according to the invention byirradiating them with polarised light. The measured values of the changein birefringence range between 0.05 and 0.08.

[0078] The light which is preferably used is linearly polarised light,the wavelength of which falls within the region of the absorption bandsof the side groups.

[0079] The production of side group monomers and the polymerisationthereof can be effected by methods which are known from the literature;see, for example, Makromolekulare Chemie 185, 1327-1334 (1984). SU 887574, Europ. Polym. J. 18, 651 (1982) and Liq. Cryst. 2. 195 (1987), DD276 297, and DE-OS 28 31 909 and 38 08 430. The polymers according tothe invention are generally produced by radical-initiated polymerisationin suitable solvents, e.g. in aromatic hydrocarbons such as toluene orxylene, in aromatic halogenated hydrocarbons such as chlorobenzene, inethers such as tetrahydrofuran or dioxane, in ketones such as acetone orcycloohexanone, and/or in dimethylformamide, in the presence ofradical-forming polymerisation initiators, e.g. azobis(isobutyronitrile)or benzoyl peroxide, at elevated temperatures, generally from 40 to 70°C., if possible under water and with the exclusion of light. They can beisolated by precipitation in suitable media, e.g. methanol. The productscan be purified by re-precipitation, e.g. with chloroform/methanol.

[0080] Isotropic films can be produced without costly orientationprocesses being necessary for which external fields and/or surfaceeffects are required. They can be produced on substrates, byspin-coating, immersion, casting or by other coating methods which areeasily controlled technologically, by pressing or flowing them betweentransparent plates, or can readily be produced as self-supporting filmsby casting or extrusion. Films such as these can be produced by suddencooling, i.e. by employing a cooling rate >100 K/min, or can also beproduced by rapidly stripping the solvent from liquid crystallinepolymers which contain structural elements of the type described above.

[0081] The film thickness of films such as these preferably rangesbetween 0.1 μm and 1 mm, particularly between 0.1 and 100 μm.

[0082] When they are in their glassy state, the side group polymersaccording to the invention are optically isotropic, amorphous,transparent and do not scatter light, and are capable of formingself-supporting films.

[0083] However, they are preferably deposited on support materials, forexample on glass or on plastics films. This can be effected by variousknown techniques, wherein the process is selected accordingly, dependingon whether a thick or a thin film is required. Thin films can beproduced, for example, by spin-coating or by doctor blade from solutionsor from the melt, thicker layers can be produced by fillingprefabricated cells, or by melt pressing or extrusion methods.

[0084] The polymers can be used for the storage of digital or analoguedata in the widest sense, e.g. for optical signal processing, forFourier transformation and convolution or for the coherent opticalcorrelation technique. The lateral resolution is limited by thewavelength of the light used for writing. It enables a pixel size from0.45 to 3000 μm to be obtained. A pixel size from 0.5 to 30 μm ispreferred.

[0085] This property makes the polymers particularly suitable for theprocessing of images and for information processing by means ofholograms, the reproduction of which can be effected by illuminationwith a reference beam. Similarly, the interference pattern ofmonochromatic light sources with a constant phase relationship can bestored. Three-dimensional holographic images can be storedcorrespondingly. Read-out is effected by illuminating the hologram withmonochromatic coherent light. A storage density Which is higher thanthat of a purely binary system can be achieved due to the relationshipbetween the electric vector of the light and the preferred direction,which is associated therewith, in the storage medium. In analoguestorage, values of the grey scale can be continuously adjusted, as canthe local resolution thereof. Read-out of stored analogue information iseffected in polarised light, wherein a negative or positive image can beretrieved depending on the position of the polarisers. The contrastbetween two polarisers which is produced by the phase shift between theordinary and the extraordinary beam can firstly be used, wherein theplanes of the polarisers advantageously form an angle of 45° to theplane of polarisation of the inscribing light and the plane ofpolarisation of the analyser is either perpendicular or parallel to thatof the polariser. Another possibility is the detection of the angle ofdeviation of the read-out light which is caused by the inducedbirefringence.

[0086] The polymers can be used as optical components which can bepassive or which can be actively switchable, particularly forholographic optics. Thus the high extent of light-induced opticalanisotropy can be used for the electrical modulation of the intensityand/or of the state of polarisation of light. Components which haveimaging properties which are comparable with those of lenses or gratingscan accordingly be produced from a polymer film by a holographicstructuring process.

[0087] Therefore, the present invention further relates to the use ofthe polymers described above for optical components.

[0088] Monomers IX are novel. Therefore, the present invention alsorelates to monomers IX.

[0089] Monomers IX can be produced by analogy with known reactions, e.g.by

[0090] A) the reaction of acid chlorides of formula

[0091]  with 4-amino-binucleus compounds, e.g. 4-aminoazobenzenes, toform monomer IX, e.g. to form the compound of Example 2.1.1;

[0092] B) 1. By the condensation of

[0093] a) 1,4-diamino nuclei, e.g. 1,4-phenylenediamine, with

[0094] b) nucleus-acid chlorides, e.g. p-nitrobenzoyl chloride, to form

[0095] c) a p-(nucleus-carboxamino)-nucleus-amine, e.g.N-(p-nitrobenzoyl)-1,4-phenylenediamine

[0096] 2. Diazotisation of 1 c) and

[0097] 3. Coupling with a compound of formula

[0098]  e.g. (meth)acrylic acid-1-(N-methylanilino)-ethyl ester, to formmonomer IX, e.g. to form the compound of Example 2.4;

[0099] C) 1. diazotisation of a 4-amino binucleus, e.g.4-aminoazobenzene,

[0100] 2. Coupling with the (meth)acrylic acid ester

[0101]  e.g. with (meth)acrylic acid-1-N-methylanilino)-ethyl ester, toform monomer IX, e.g. to form the diazo compound of Example 2.5.

[0102]1-1,2 mol of the aminobinuclear compound per mol of acid chlorideis preferably used for reaction A. The reaction can be conducted insolvents, wherein inert organic solvents comprising ethers, e.g.dioxane, are preferred. The reaction is preferably conducted attemperatures from 20 to 80° C.

[0103] The diazotisations for reactions B and C can be conducted inmineral acids such as hydrochloric acid, sulphuric acid or phosphoricacid for example, or can be conducted in carboxylic acids such as aceticacid or propionic acid, with sodium nitrite or nitrosylsulphuric acid asthe nitrosylating agent, preferably at temperatures from −10 to +20,particularly 0 to +10° C. In general, the coupling component is placedin a vessel, optionally in a suitable solvent such as glacial aceticacid or methanol, the pH is adjusted to a value from 1 to 6, preferablyfrom 3 to 4, and the temperature during the addition of the diazoniumcomponent is maintained at 0 to 30, preferably 5 to 10° C. The batch isthen neutralised, with caustic soda or aqueous sodium carbonate solutionfor example, and is diluted with water, and the precipitated product isfiltered off under suction.

[0104] The percentages given in the following examples are percentagesby weight in each case unless indicated otherwise.

EXAMPLES Example 1 Preparation of Polymers

[0105] 1.1 Preparation of Monomers

H₂C═C(CH₃)—COO—CH₂—CH₂—Q—E

[0106] 1.1.1.

[0107] 31.4 g 2.4-dicyanoaniline were diazotised with 72 gnitrosylsulphuric acid at 0 to 5° C. in 300 ml of 50% aqueous sulphuricacid and the batch was subsequently stirred for 1 hour. The reactionmixture was slowly added to a solution of 20.4 g aniline and 4.5 g ureain 300 ml 50% aqueous sulphuric acid, the temperature being held at 0°C. After stirring for a further 1 hour, the pH of the reaction mixturewas adjusted to 5.5 with sodium carbonate, and the precipitate wasfiltered off under suction, washed with water, and dried. 34 g of red4-amino-2′,4′-dicyano-azobenzene were obtained. The product was usedfurther without purification.

[0108] 27.6 g 4-amino-2′,4′-dicyano-azobenzene in 500 ml dioxane wereadded to a solution of 33 g 4-(2-methacryloyloxy)-ethoxy-benzoic acidchloride in 100 ml dioxane, the batch was stirred for 2 hours, and theproduct was precipitated by pouring the solution into 2 liters of water.The precipitate was filtered off under suction, dried, and purified bycrystallising it twice from dioxane. The yield corresponded to 30.4 g oforange-red crystals with a f.p. of 215-217° C. λ_(max)=404.5 nm (DMF).

[0109] 20.7 g 2,4-dicyanoaniline were diazotised with 48 gnitrosylsulphuric acid at 0 to 5° C. in a solution comprising 200 mlglacial acetic acid, 40 ml of 85% phosphoric acid and 7.5 ml ofconcentrated aqueous sulphuric acid, and the batch was subsequentlystirred for 1 hour. The reaction mixture was slowly added to a solutionof 16 g phenol and 3 g urea in 120 ml water, the temperature being heldat 10° C. and the pH being maintained at 6.3-6.5 with caustic sodasolution. After stirring for a further 1 hour, the precipitate wasfiltered off under suction, washed with water, dried, and recrystallisedfrom toluene. 30.3 g of orange-red 4-hydroxy-2′,4′-dicyano-azobenzenewere obtained.

[0110] A solution of 18.1 g of 4-(2-methacryloyloxy)-ethoxy-benzoic acidchloride in 100 ml diethyl ether was slowly added to a solution of 16.6g 4-hydroxy-2′,4′-dicyano-azobenzene and 11 ml triethylamine in 400 mlTHF, with the temperature being held at 5° C. The batch was stirred atroom temperature overnight, and the reaction solution was thereaftertreated with 500 ml chloroform and was shaken 5 times with 300 ml watereach time. The organic phase was dried over anhydrous magnesiumsulphate. After distilling off the solvent, the solid residue wasrecrystallised from ethanol. 21.6 g of orange-red crystals wereobtained, which had an f.p. of 172-173° C. λ_(max)=349 nm (DMF).

[0111] 12 g 3,4-dicyanoaniline were diazotised analogously to 1.1.2. Thereaction mixture was slowly added, at 0 to 5° C., to a solution of 6.5 ganiline in 60 ml glacial acetic acid, and was stirred at roomtemperature overnight. The precipitate was filtered off under suction,washed with water and dried. 12 g of red4-amino-3′,4′-dicyano-azobenzene were obtained, and were used furtherwithout purification. The further synthesis of the monomer was effectedanalogously to 1.1.1. Monomer 1.1.3 had an f.p. of 160-161° C. andλ_(max)=392 nm (DMF).

[0112] This monomer was prepared analogously to 1.1.3. It had an f.p. of207-208° C. and λ_(max)=456 nm (DMF).

[0113] a) 38.6 g 4-(4-nitrobenzoylamino)-aniline were dissolved in amixture of 207 ml glacial acetic acid. 72 ml propionic acid and 3 ml of30% hydrochloric acid. 49.7 g of 40% nitrosylsulphuric acid were addedthereto at 0-5° C. over 1 hour. The batch was then stirred for a further2 hours at 0-5° C.

[0114] b) 32.8 g N-methyl-N-(2-methacryloyloxy-ethyl)-aniline (method1.1.6) were dissolved in 130 ml glacial acetic acid. The diazotisationsolution from a) was added thereto at 5-10° C. over 1 hour, the pH beingmaintained at 3 by the drop-wise addition of 20% aqueous sodiumcarbonate solution. The batch was subsequently stirred overnight at a pHof 3. The suspension was filtered off under suction. The product, whichwas still moist, was suspended in 500 ml water. The pH was increased to7 by adding 20% aqueous sodium carbonate solution. The product was againfiltered off under suction, washed with 200 ml water and dried undervacuum at 50° C. 56.2 g (77% theoretical) of an orange-red powder wereobtained, which had an f.p. of 198° C. In DMF, the product exhibited anabsorption maximum at 430 nm and a shoulder at 447 nm.

[0115] N-methyl-N-(2-methacryloyloxy-ethyl)-aniline was prepared in thefollowing manner:

[0116] from methacrylic chloride:

[0117] 100 g N-methyl-N-(2-hydroxyethyl)-aniline were dissolved in 100ml chloroform. 182.6 g triethylamine and 137.2 g methacrylic chloridewere slowly added drop-wise thereto at 40° C., with stirring, and thebatch was stirred at 40° C. overnight. Thereafter, the reaction solutionwas treated with 500 ml chloroform and was shaken 5 times with 200 mlwater each time. The organic phase was dried over anhydrous magnesiumsulphate, treated with copper(I) chloride, and, after distilling off thesolvent, was distilled under high vacuum. The methacrylic ester ofhydroxyethylaniline distilled over at 127-130° C./55 mbar as a liquidwhich was as clear as water. The yield was 49.5 g.

[0118] from methacrylic acid:

[0119] 50 ml of conc. sulphuric acid were added drop-wise at roomtemperature, with stirring, to a solution of 100 mlN-methyl-N-(2-hydroxyethyl)-aniline, 265 ml methacrylic acid and 26.5 ghydroquinone in 398 ml chloroform. After standing overnight, the batchwas heated and the water of reaction was removed azeotropically. Aftercooling, the pH was adjusted to between 7 and 8 with concentratedaqueous sodium carbonate solution, and the product was extracted fromthis solution by shaking with ether. The further procedure was asdescribed above, and resulted in a yield of 56 g.

[0120] 2-methyl-4-amino-2′,4′-dicyanoazobenzene was synthesisedanalogously to 1.1.3 from 2,4-dicyano-aniline and o-toluidine. 4.1 g2-methyl-4-amino-2′,4′-dicyanoazobenzene were diazotised analogously to1.1.2.

[0121] The reaction mixture was slowly added to a mixture of 3.5 gmethyl-N-(2-methacryloyloxy-ethyl)-aniline and 5 g sodium carbonate in100 ml methanol, whilst maintaining the temperature at 10° C. andmaintaining the pH at 5 with sodium carbonate. The orange-colouredby-product was first precipitated and was filtered off. Thereafter, thereaction mixture was treated with a fresh portion of sodium carbonate.After some time, a violet precipitate was produced. This was filteredoff, washed with water and dried. 2.1 g of a violet product wereobtained, which had an f p. of 163-165° C. and for which λ_(max)=536 nm(DMF).

[0122] 2-methyl-4-amino-2′,4′-dicyanoazobenzene (method 1.1.6) wasreacted with 4-(2-methacryloyloxy)ethoxy-benzoic acid chlorideanalogously to 1.1.1. Orange-coloured crystals were obtained, which hadan f.p. of 182-184° C. and for which λ_(max)=389 nm (DMF).

[0123] 4-amino-4′-dimethylaminoazobenzene was reacted with4-(2-methacryloyloxy)-ethoxy-benzoic acid chloride analogously to 1.1.1.Orange-coloured crystals were obtained, which had an f.p. of 218 220° C.and for which λ_(max)=428 nm (DMF).

[0124] 4-amino-4′-nitroazobenzene (disperse orange 3) was reacted with4-(2-methacryloyloxy)-ethoxy-benzoic acid chloride analogously to 1.1.1.Orange-coloured crystals were obtained, which had an f.p. of 202° C. andfor which λ_(max)=391 nm (DMF).

[0125] 8.6 g 4-cyanoaniline were diazotised, analogously to 1.1.2. Thereaction mixture was slowly added at 5 to 10° C. to a solution of 6.5 ganiline and 3 g urea in 60 ml water and was stirred at room temperatureovernight. The precipitate was filtered off under suction, washed withwater and dried. 6.9 g of the orange-coloured4-imino-4′-cyano-azobenzene were obtained, and were used further withoutpurification. The further synthesis of the monomer was effectedanalogously to 1.1.1. Monomer 1.1.10 had an f.p. of 174° C., andexhibited a liquid crystalline phase up to 204° C.; λ_(max)=380 nm(DMF).

[0126] 7 g 4-(5-nitro-2-thiazolylazo)aniline (method 1.1.4) wwerediazotised, analogously to 1.1.2. The reaction mixture was slowly addedto a solution of 6.2 g N-methyl-N-(2-methacryloyloxy-ethyl)-aniline and1 g urea in 30 ml of glacial acetic acid, whilst the temperature wasmaintained at 10° C. After stirring for a further 1 hour, the reactionmixture was poured on to ice. The precipitate was filtered off, washedwith water and dried. 10.1 g of dark blue crystals were obtained, whichhad an f.p. of 207° C. and for which λ_(max)=589 nm (DMF).

[0127] 2-methyl-4-amino-3′,4′-dicyano-azobenzene (method 1.1.6) wasreacted with Nmethyl-N-(2-methacroyloxy-ethyl)-aniline, analogously to1.1.1. Violet crystals were obtained, which had an f.p. of 164° C. andfor which λ_(max)=521 nm (DMF).

[0128] 2,5-dimethyl-4-amino-2′,4′-dicyano-azobenzene was synthesisedfrom 2,4-dicyanoaniline and 2,5-dimethylaniline, analogously to 1.1.3.

[0129] 5.5 g 2.5-dimethyl-4-amino-2′,4′-dicyano-azobenzene in 200 mldioxane were added to a solution of 5.9 g4-(2-methacryloyloxy)-ethoxy-benzoic acid chloride in 40 ml dioxane, thebatch was boiled under reflux for 48 hours with stirring, and theproduct was precipitated by pouring the solution into water. Theprecipitate was filtered off under suction, dried, and purified byrecrystallising it twice from dioxane. The yield was 6.0 g of orange-redcrystals with an f.p. of 200-202° C. λ_(max)=367.5 nm (DMF).

[0130] 1.2 Preparation of the Homopolymer

[0131] 7.9 g monomer 1.1 were polymerised at 70° C. in 75 ml DMF, underargon as a protective gas, and using 0.39 g azobis(isobutyronitrile) asthe polymerisation initiator. After 24 hours, the batch was filtered,the DMF was distilled off, and the residue was boiled with methanol toremove unreacted monomer and was dried at 120° C. under high vacuum.7.18 g of an amorphous polymer were obtained, which had a glasstransition temperature of 150° C. and the optical properties of whichare given in Example 2.1.1.

[0132] An analogous procedure was employed for the production of otherpolymers.

Example 2 Production of Light-Induced Birefringence

[0133] Production of test samples: glass plates of size 2×2 cm andthickness 1.1 mm were placed in a spin coater (Suss RC 5 type ofconstruction) and were coated with 0.2 ml of a solution of 150 g of thepolymers listed below in 1 liter of absolute tetrahydrofuran at 2000 rpmfor 10 seconds. The film was 0.9 μm thick, transparent and amorphous.The surface appeared uniformly dark between crossed polarisers indaylight.

[0134] The test plates were exposed using an Ar ion laser with an outputof 60, 120 or 250 mW at a wavelength of 514 nm, whereupon birefringencewas observed. The maximum birefringence An which could be obtained inthe polymer film was determined in two steps:

[0135] Firstly, the maximum inducable path difference Δλ which produceda brightening effect between crossed polarisers was determined by ameasurement using an Ehringhaus compensator. A quantitativedetermination was made by compensating for the brightening effect. Thiswas effected by rotating a quartz crystal which had been moved into thebeam path and which altered the optical path length and thus the pathdifference. The path difference at which the brightening effect wasfully compensated for was then determined. This measurement had to bemade using light of a wavelength outside the absorption range of thecompounds, in order to avoid resonance effects. As a rule, a He—Ne laserwith an emission wavelength of 633 nm is satisfactory. For long-waveabsorptions, measurements are made using a diode laser of wavelength 820nm. The read-out wavelength employed is given in the following Tablesunder the column heading “λ”.

[0136] In a second step, the film thickness of the polymer was measuredusing a film thickness measuring instrument with a mechanical mode ofaction (Alphastep 200; manufactured by Tencor Instruments).

[0137] The change in birefringence Δn was determined from the quotientcomprising the path difference Δλ divided by the film thickness d:${\Delta \quad n} = \frac{\Delta\lambda}{d}$

[0138] The absorption maxima were determined by evaluating theUV/visible absorption spectra. Formula 1

Example 2.1 ν_(A) Δn mW λ[nm] 2.1.1 X = NH 25380 0.278 60 633 2.1.2 X =O 29200 0.134 60 633

[0139] Formula 2

Example 2.2 ν_(A) Δn mW λ[nm] 26000 0.244 250 820

[0140] Formula 3

Example 2.3 ν_(A) Δn mW λ[nm] 23800 0.094 120 820

[0141] Formula 4

Example 2.4 ν_(A) Δn mW λ[nm] 20800 0.233 250 633

[0142] Formula 5

Example 2.5 ν_(A) Δn mW λ[nm] 27855; 19380 0.194 250 820

[0143] Formula 6

Example 2.6 ν_(A) Δn mW λ[nm] 26000 0.097 250 820

[0144] Formula 7

Example 2.7 ν_(A) Δn mW λ[nm] 25000 0.127 250 820

[0145] Formula 8

Example 2.8 ν_(A) Δn mW λ[nm] 27400 0.145 250 820

1. Homopolymers of monomers which contain groupings which have at leastthree rings, which can absorb the electromagnetic radiation of visiblelight and are constricted so that, in a thermodynamically stable state,they are extended and highly anisormetric, where these groupings whichhave at least three rings have at least one electron-withdrawingsubstituent which gives rise to a dipole moment which forms an angle ofat least 20° with the longitudinal axis of the groupings which have atleast three rings.
 2. Homopolymers according to claim 1, which carry, ona main chain acting as backbone, branching off from the same, covalentlyconnected side groups of the formula —S—T—Q—E where S is oxygen, sulphuror NR¹, R¹ is hydrogen or C₁-C₄-alkyl, T is the radical (CH₂)_(n), whichmay be interrupted if desired by —O—, —NR¹— or —OSiR¹ ₂O— and/or may besubstituted if desired by methyl or ethyl, n is the number 2, 3 or 4, Qis g bivalent radical and, E is a grouping which has at least threerings as defined in claim
 1. 3. Process to prepare homopolymersaccording to claims 1 and 2, by homopolymerizing monomers which containgroupings which have at least three rings, which can absorb theelectromagnetic radiation of visible light and are constructed so that,in a thermodynamically stable state, they are extended and highlyanisometric, where these groupings which have at least three rings haveat least one electron-withdrawing substituent which gives rise to adipole moment which forms an angle of at least 20° with the longitudinalaxis of the groupings which have at least three rings.
 4. Monomers ofthe formula

where R is hydrogen or methyl and S, T, Q and E are as defined in claim2.
 5. Process according to claim 3, in which monomers according to claim4 are homopolymerized.
 6. Use of the homopolymers according to claims 1and 2 to produce films and coatings.
 7. Use of the homopolymersaccording to claims 1 and 2 to produce optical components for opticalstorage of information and for holography.